In the past, rotors have been used to generate a liquid spray. Although such rotors have been used in connection with pipe coaters (see U.S. Pat. No. 3,719,168), liquid atomizers (see U.S. Pat. No. 2,902,223) and dishwashers (see U.S. Pat. No. 3,444,870) in which the liquid can be sprayed indiscriminately into the air or onto articles, such as pipe interiors and dishes, they have not been used in environments in which the liquid cannot be sprayed indiscriminately.